U.S. patent application number 13/207475 was filed with the patent office on 2012-04-19 for metal detector and ground-penetrating radar hybrid head and manufacturing method thereof.
Invention is credited to Ali ETEBARI, Mark Hibbard, Brian A. Whaley, Jason Wolfson.
Application Number | 20120092206 13/207475 |
Document ID | / |
Family ID | 45605613 |
Filed Date | 2012-04-19 |
United States Patent
Application |
20120092206 |
Kind Code |
A1 |
ETEBARI; Ali ; et
al. |
April 19, 2012 |
METAL DETECTOR AND GROUND-PENETRATING RADAR HYBRID HEAD AND
MANUFACTURING METHOD THEREOF
Abstract
A hybrid ground penetrating radar (GPR)/metal detector (MD) head
includes a V-dipole GPR antenna and transmit and receive MD coils.
One of the MD coils is arranged in a quadrupole configuration with
a crossbar, and the V-dipole antenna is perpendicular to the
crossbar. The legs of the V-dipole antenna may straddle the
crossbar or may be on one side of the crossbar. The MD coils may be
fabricated on a printed circuit board, which may be at a non-normal
angle with respect to a central axis of the V-dipole antenna.
Inventors: |
ETEBARI; Ali; (Ashburn,
VA) ; Wolfson; Jason; (Chantilly, VA) ;
Whaley; Brian A.; (Vienna, VA) ; Hibbard; Mark;
(Arlington, VA) |
Family ID: |
45605613 |
Appl. No.: |
13/207475 |
Filed: |
August 11, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61375624 |
Aug 20, 2010 |
|
|
|
Current U.S.
Class: |
342/22 ; 29/601;
324/326 |
Current CPC
Class: |
G01V 3/101 20130101;
G01S 13/885 20130101; G01V 3/165 20130101; Y10T 29/49018 20150115;
G01V 3/105 20130101; G01V 3/12 20130101 |
Class at
Publication: |
342/22 ; 324/326;
29/601 |
International
Class: |
G01S 13/86 20060101
G01S013/86; H05K 13/00 20060101 H05K013/00; G01V 3/08 20060101
G01V003/08 |
Claims
1. A ground penetrating radar ("GPR") and metal detector ("MD")
hybrid head comprising: an MD sensor including at least one receive
coil in a quadrupole configuration including a crossbar, and at
least one transmit coil, the crossbar having a first axis parallel
to a direction in which current flows in the crossbar; and at least
one GPR V-dipole antenna arranged in a plane perpendicular to the
first axis of the crossbar so as to reduce coupling between the
coils of the MD sensor and the antenna; wherein the transmit coil
has an outer perimeter, the receive coil has an outer perimeter,
and wherein at least a portion of the V-dipole antenna is within a
cylinder formed by the projection of one of the outer perimeter of
the receive coil or the transmit coil onto a plane perpendicular to
a central axis of the V-dipole antenna.
2. The hybrid head of claim 1, further including at least one
electrostatic shield covering the top and bottom portion of the
transmit and receive coils so as to stabilize capacitance between
the transmit and receive coils and the changing external
environment.
3. The hybrid head of claim 1, wherein the at least one receive
coil is concentric with the at least one transmit coil.
4. The hybrid head of claim 3, wherein each of the at least one
transmit coil and the at least one receive coil includes a
plurality of turns respectively, the plurality of turns being
concentric to each other and offset along an axis of
concentricity.
5. The hybrid head of claim 3, wherein the at least one V-dipole
antenna is located within one half of the MD sensor on one side of
the crossbar.
6. The hybrid head of claim 3, where first and second conductors of
the at least one V-dipole antenna are placed on opposite sides of
the crossbar.
7. The hybrid head of claim 3, wherein the MD coils are pitched at
an angle between 20 and 90 degrees with respect to a central axis
of the V-dipole antenna.
8. The hybrid head of claim 1, wherein the at least one transmit
coil and the at least one receive coil are formed on a printed
circuit board ("PCB.")
9. The hybrid head of claim 8, wherein the PCB has at least one
layer including at least one turn of the transmit coil and at least
one turn of the receive coil.
10. The hybrid head of claim 8, wherein the PCB includes multiple
layers, each of the layers including at least one turn of the
transmit coil and at least one turn of the receive coil, wherein
the at least one turn of the transmit coil and the at least one
turn of the receive coil are approximately concentric and wherein
the concentric layers which are arranged in stacked planes which
are offset from each other along an axis of concentricity.
11. The hybrid head of claim 8, wherein the at least one V-dipole
antenna is located within one half of the MD receive coil on one
side of the crossbar.
12. The hybrid head of claim 8, where first and second conductors
of the at least one V-dipole antenna are placed on opposite sides
of the crossbar.
13. The hybrid head of claim 8, wherein the MD coils are pitched at
an angle between 20 and 90 degrees with respect to a central axis
of the V-dipole antenna.
14. The hybrid head of claim 1, further comprising a housing,
wherein the MD sensor and the GPR antenna are mechanically
connected to the housing.
15. A method for manufacturing an MD/GPR hybrid head, the method
comprising the steps of: forming an MD sensor including at least
one receive coil in a quadrupole configuration including a
crossbar, and at least one transmit coil, the crossbar having a
first axis parallel to a direction in which current flows in the
crossbar; and positioning at least one GPR V-dipole antenna in a
plane perpendicular to the first axis of the crossbar so as to
reduce coupling between the coils of the MD sensor and the antenna;
wherein the transmit coil has an outer perimeter, the receive coil
has an outer perimeter, and wherein at least a portion of the
V-dipole antenna positioned within a cylinder formed by the
projection of one of the outer perimeter of the receive coil or the
transmit coil onto a plane perpendicular to a central axis of the
V-dipole antenna.
16. The method of claim 15, further including the step of covering
the top and bottom portion of the transmit and receive coils with
at least one electrostatic shield so as to stabilize capacitance
between the transmit and receive coils and the changing external
environment.
17. The method of claim 15, wherein the at least one receive coil
is concentric with the at least one transmit coil.
18. The method of claim 15, wherein the at least one V-dipole
antenna is positioned within one half of the MD sensor on one side
of the crossbar.
19. The hybrid head of claim 3, where first and second conductors
of the at least one V-dipole antenna are placed on opposite sides
of the crossbar.
20. The hybrid head of claim 3, wherein the MD coils are pitched at
an angle between 20 and 90 degrees with respect to a central axis
of the V-dipole antenna.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and derives the benefit of the
filing date of U.S. patent application Ser. No. 61/375,624, filed
Aug. 20, 2010. The entire content of this application is herein
incorporated by reference in its entirety.
FIELD
[0002] The present disclosure is directed to the field of mine and
metal detection and, more particularly, towards systems and methods
for integrating a ground penetrating radar head with a metal
detector head.
BRIEF DESCRIPTION OF THE FIGURES
[0003] FIG. 1 is a schematic representation of the transmit and
receive coils of an electromagnetic induction metal detector head
according to a disclosed embodiment.
[0004] FIG. 2 is a schematic representation of an integrated ground
penetrating radar head according to a disclosed embodiment.
[0005] FIGS. 3A-3D are schematic representations of layers in a
multi-layer printed circuit board constituting the transmit and
receive coils of a metal detector head according to an alternate
disclosed embodiment.
[0006] FIGS. 4A-4F are schematic representations of layers in a
multi-layer printed circuit board constituting the transmit and
receive coils of a metal detector head according to an alternate
disclosed embodiment.
[0007] FIG. 5A-5C are top view, front view, and side view schematic
representations of an integrated ground penetrating radar head
according to an alternate disclosed embodiment.
[0008] FIG. 6 is a block diagram of a hybrid head including a
printed circuit board implementation of transmit and receive coils
and a ground penetrating radar antenna mechanically connected to a
housing according to an alternate disclosed embodiment.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0009] A need has arisen for a hand held sensor that can detect
underground objects, including but not limited to underground
objects such as land mines. The sensor must be unintrusive because
of the nature of certain underground objects such as land mines.
The combination of ground penetrating radar ("GPR") and metal
detection ("MD", also referred to herein as electromagnetic
induction, "EMI", sensing) is desirable because of the different
material characteristics that they detect. A GPR system can measure
the difference between dielectric constants of materials and their
relative positions, while the MD measures the nearby presence or
absence of conductive materials, with some information about the
size and shape.
[0010] Integrating the MD sensor coils and the GPR antenna into a
single, hybrid head can cause problems because both the transmit
and receive coils of the EMI sensor and the antenna of the GPR
produce and/or sense electro-magnetic fields that may be affected
by the proximity of the other, thereby affecting the operation of
MD, the GPR, or both. For example, coupling of the MD coils to the
GPR signal may result in ringing (clutter) in the GPR system, which
may lower sensitivity and degrade performance. Accordingly, it is
desirable to reduce coupling (resonance) between EMI sensor coils
and GPR antennas. This can be achieved through both positioning of
the coils and antennas relative to each other and through the
choice of materials used to fabricate the antennas and coils in the
hybrid head.
[0011] At a high level, this disclosure is directed to a GPR and MD
hybrid head. In some embodiments, the hybrid head includes at least
one GPR antenna, an MD transmit coil, and a MD receive coil that is
arranged in a quadrupole configuration including a crossbar to
minimize coupling between the transmit and receive coils, similar
to common mode rejection. The at least one GPR antenna is a planar
antenna, such as a V-dipole, that is positioned in a plane
perpendicular to the crossbar of the quadrupole receive coil of the
MD coils so as to reduce coupling between the GPR antenna and the
MD coils. In some embodiments, in order to further reduce coupling
between the GPR antenna and the MD transmit and receive coils, the
plane in which the MD transmit and receive coils is located is
positioned at a non-normal angle between 20 and 90 degrees, and
more particularly between 45 and 90 degrees, such as 70 degrees,
with respect to a central axis of the GPR planar antenna.
[0012] The details of the design and implementation of an MD sensor
in a quadrupole configuration are discussed in at least the
following papers, all of which are hereby incorporated by reference
in their entirety in this application: "Broadband Electromagnetic
Induction Sensor for Detecting Buried Landmine," Waymond R. Scott,
Jr.; "New Cancellation Technique for Electromagnetic Induction
Sensors," Waymond R. Scott, Jr.; and Michael Malluck; "Broadband
Array of Electromagnetic Induction Sensors for Detecting Buried
Landmines," Waymond R. Scott, Jr.; "Location Estimation Using A
Broadband Electromagnetic Induction Array," Ali C. Gurbuz, Waymond
R. Scott, Jr., and James H. McClellan; "Beamforming Array for
Detecting Buried Land Mines," Seung-Ho Lee and Waymond R. Scott,
Jr.; "Combined Seismic, Radar, and Induction Sensor for Landmine
Detection," Waymond R. Scott, Jr.; Kangwook Kim, Gregg D. Larson,
Ali C. Gurbuz, and James H. McClellan; and "Performance Comparison
of Frequency Domain Quadrupole and Dipole Electromagnetic Induction
Sensors in a Landmine Detection Application," Eric B. Fails, Peter
A. Torrione, Waymond R. Scott, Jr., and Leslie M. Collins.
[0013] In addition to the MD sensor arranged in a quadrupole
configuration, the hybrid head also includes a V-dipole antenna of
a GPR collocated with the MD sensor. The details of the design and
implementation of a V-dipole antenna for a GPR are provided in the
papers cited above. Details concerning the design and
implementation of V-dipole antennas are also disclosed in Kim et
al., "The Design and Realization of a Discreetly Loaded Resistive
Vee Dipole on a Printed Circuit Board", 2003, pp. 818-829; Vol.
5089, Proceedings of SPIE, which is also incorporated by reference
in its entirety in this application.
[0014] While the configuration discussed above may reduce most of
the coupling between the MD sensor and the GPR antenna, there may
be some coupling due to components of the MD coils that may be
oriented parallel to the to the V-dipoles. This coupling may be
reduced by pitching the MD sensor coils at a non-normal angle with
respect to the plane of the GPR antenna as discussed above.
[0015] Furthermore, in an embodiment the top and bottom portion of
the transmit and receive coils of the MD sensor may be covered by
an electrostatic shield. The electrostatic shield fixes the
capacitance of the coil to a changing outside environment.
[0016] A particular embodiment of an MD/GPR hybrid head will now be
discussed with reference to FIGS. 1 and 2. FIG. 1 illustrates a low
radar cross section transmit/receive coil assembly 100. The coil
assembly 100 is formed from two D-shaped halves 10, 20. Each of the
halves 10, 20 is formed from a substrate 30 on which a plurality of
traces 40 are formed. The substrate 30 may be formed from a
flexible material such as a polyester or polyimide. The traces 40
may be formed of conducting, metallic material such as copper using
any known technique, such as chemical etching. Connectors 50
connect the traces on the two halves 10, 20 such that the current
in the receive coil flows in a figure eight pattern through
multiple turns of the coil assembly 100, with current flowing
through all of the traces 40 on the crossbar 60 in the same
direction (referred to in the art as a quadruple configuration).
For example, in one embodiment, the connectors 50 connect the
traces 40 such that current flows in the direction of the sequence
of arrows A-B-C-D through one turn of the coil assembly 100. The
transmit coil extends around the outer circumference of both halves
10, 20 on the outside or inside of substrates 30. The substrates 30
and the traces 40 are as thin as possible consistent with
structural and electrical requirements in order to minimize the
radar cross section of the coil assembly 100. Alternatively, the
transmit coil may be formed in a simple circular pattern on a
separate substrate surrounding the receive coil such that the
receive coil is concentric with the transmit coil.
[0017] Referring now to FIG. 2, a GPR antenna array 200 including a
plurality of elements 210 is shown (3 elements are shown in FIG. 2,
but those of skill in the art will recognize that more or less
elements may be used). The elements 210 are each planar and in the
shape of an inverted V-dipole, with the open end of the V-dipole
positioned over the crossbar 60 of the coil assembly 100. In this
manner, the components of the coil assembly 100 that are along the
B-field axis (i.e., the crossbar 60) do not couple to the V-dipoles
210 which define the E-field axis. The elements 210 may be formed
on a planar substrate 212 with a metallic trace 220 formed thereon.
In FIG. 2, the distal ends (the ends at the open end of the V) of
the V-dipole elements 210 are positioned such that the crossbar 60
is interposed between them. In other embodiments, the V-dipole
elements 210 are positioned such that no portion of the crossbar 60
is interposed between any portion of the two legs of the V-dipole
elements 210, but the distal ends of the V-dipole elements are on
opposite sides of the plane in which crossbar 60 is oriented. In
such configurations, the V-dipole elements are within an imaginary
cylinder C (as used herein, "cylinder" is not limited to circular
cylinders but rather includes any surface generated by a straight
line intersecting and moving along a closed plane curve while
remaining parallel to a fixed straight line that is perpendicular
to the closed plane curve) with a base formed by the projection of
the cross sectional shape of the coil assembly 100 onto the plane
which is perpendicular to the planes in which the crossbar 60 and
the V-dipole elements 210 are oriented.
[0018] A second embodiment of an MD/GPR hybrid head 300 will now be
discussed with reference to FIGS. 3A-D and 5A-C. The receive and
transmit coils of the hybrid head 300 are formed by a multilayer
PCB (printed circuit hoard) with through-hole vias for inter-layer
connections. Each layer of the multi-layer PCB board includes
either four grounding (shielding) fingers or two turns each of both
the transmit and receive coils. The transmit and receive coils are
approximately concentric (as used herein, approximately concentric
means that the approximate centers of the receive and transmit
coils are both approximately on an axis of concentricity that is
normal to the faces of the coils, and one coil is located within an
outer perimeter, formed by the turns of the other coil). Also, as
above, the receive coil is in a quadrupole configuration. The total
numbers of layers included in the PCB board depends upon the number
of turns desired.
[0019] FIGS. 3A-D illustrate various layers of the PCB. FIG. 3A
illustrates a top grounding (shielding) layer 301 with four
grounding fingers formed by a long trace 302 connected to the
ground terminal that covers the inner and outer areas of the PCB,
and a short trace 304 connected to the Rx- (receive coil negative)
terminal and the through hole via 306. FIG. 3B illustrates a bottom
grounding layer 307 with four grounding fingers formed by the long
trace 308, and a short trace 310 connected to the Rx+ (receive coil
positive) terminal. Each PCB will have one top grounding layer 301
and one bottom grounding layer 307, with one or more pairs of
complementary inner layers disposed between them. FIGS. 3C and 3D
illustrate the complementary first and second inner layer PCBs,
respectively. The first inner layer 311 illustrated in FIG. 3C
includes an outer trace 312 that forms two turns of a transmit
coil, and an inner trace 314 that forms two turns of a quadrupole
receive coil. The via 316 in FIG. 3C is aligned with the via 306 in
the top grounding layer 301 of FIG. 3A, so the trace 314 will be
electrically connected to the Rx- terminal at this point.
[0020] The second inner layer 319 illustrated in FIG. 3D also
includes an outer trace 320 that forms two turns of the transmit
coil, with one end of the trace connected to the Tx- terminal and
the other end connected to via 322 which is aligned with via 318 of
FIG. 3C, thereby connecting the two turns of the transmit coil
realized by the trace 320 in FIG. 3D to the two turns of the
transmit coil realized by the trace 312 of FIG. 3C. The second
inner layer of FIG. 3D also includes an inner trace 324 that forms
two turns of the receive coil in a quadrupole configuration. One
end of the trace 324 is connected to via 326, which aligns with via
317 of FIG. 3C, thereby connecting the two turns of the receive
coil formed by the trace 324 with the two turns of the receive coil
formed by the trace 314 of FIG. 3C. The other end of the trace 324
is connected to via 328, which aligns with via 309 of the bottom
grounding layer 307 of FIG. 3B, thereby connecting the two turns of
the receive coil formed by trace 324 with the Rx+ terminal shown in
FIG. 3B.
[0021] A four layer PCB formed by a top layer 301, a first inner
layer 311, a second inner layer 319 and a bottom layer 307, along
with suitable interconnections made using the vias discussed above,
will thus have receive and transmit coils with four turns (two
turns on each of the inner layers
[0022] When additional turns on the transmit and receive coils are
desired, additional inner PCB layers may be added. FIGS. 4A-F
illustrate an exemplary multilayer PCB with internal layers between
a top layer and a bottom layer. In order to accommodate the
interconnection between the layers, additional vias are added. In
general, 2 additional vias for the transmit coil and two additional
vias for the receive coil are needed for each pair of additional
inner layers. As with the previously discussed 4-layer embodiment,
the six-layer PCB includes a top grounding layer 401 shown in FIG.
4A with a long, four finger grounding trace 402 and a short trace
404 connected to an Rx- terminal via and a second via F. Below the
top layer 401 is an inner layer 411 shown in FIG. 4B. The inner
layer 411 includes an outer trace 412 that forms two turns of the
transmit coil, and an inner trace 414 that forms two turns of the
receive coil, again in a quadrupole configuration. The outer
transmit coil trace 412 is connected on one end to a Tx- terminal
via and at the other end to a via C. The receive coil turns 414 are
connected at one end to a via F (through which it is connected to
the Rx- terminal connection in layer 401) and to a via D on the
other end.
[0023] The next layer 419, shown in FIG. 4C, includes two turns 420
of the transmit coil connected to a via C (through which they are
connected to the transmit coil turns in layer 411) and a via A, and
two turns 422 of the receive coil connected to a via D (through
which it is connected to the receive coil turns in layer 411) and a
via H. The next layer 423, shown in FIG. 4D, includes two turns 424
of the transmit coil connected to a via A (through which they are
connected to the transmit coil turns in layer 419) and a via B, and
two turns 426 of the receive coil connected to a via H (through
which it is connected to the receive coil turns in layer 419) and a
via E. The next layer 427, shown in FIG. 4E, includes two turns 428
of the transmit coil connected to a via B (through which they are
connected to the transmit coil turns in layer 423) and a Tx+ via,
and two turns 430 of the receive coil connected to a via E (through
which it is connected to the receive coil turns in layer 423) and a
via G. The bottom layer 431 shown in FIG. 4F includes a trace 432
connected at one end to a via G (through which it is connected to
the receive coil turns in layer 427) and at the other end to a Rx+
terminal. The bottom layer 431 also includes a long trace 434
connected to a via 436 that forms four grounding fingers. Those of
skill will recognize that additional pairs of inner layers may be
added by adding additional vias for the transmit and receive coils
using the scheme of FIGS. 4A-F.
[0024] Referring now back to FIGS. 3A-D, in order to facilitate
incorporation of V-dipole antennas (as discussed further below),
the areas of the PCB marked with an X in FIGS. 3A-D inside each of
the figure-8 patterns of the receive coil may be removed to allow
the distal ends of the V-dipole antennas to be placed through the
plane of the PCB. In other embodiments in which the ends of the
V-dipole antennas are not passed through the plane of the PCB,
those areas in FIGS. 3A-D marked with an X are not removed.
[0025] The layers 301, 307, and one pair of complementary layers
311 and 319 illustrated in FIGS. 3A-D may be formed into a single
PCB 510 (with the areas of the PCB 510 marked with an X in FIGS.
3A-D removed) that forms a part of a hybrid MD/GPR head 500 as
shown in FIGS. 5A-C. Also forming part of the hybrid head 500 are
four planar V-dipole antenna elements 520. As shown most clearly in
FIG. 5B, the legs 522 of each of the antenna elements 520 extend
through the central plane (the plane parallel to the faces of the
PCB 510 and passing through its center) P of the PCB 510 such that
the distal ends of the legs 522 and the vertex V of the elements
520 are on opposite sides of the plane of the PCB 510. Referring
still to FIG. 5B, the central plane P of the PCB 510 forms an angle
y of 70 degrees with respect to the central axis Y of the V-dipole
antenna elements 520 (the central axis of the V-dipole antenna
elements is the axis that passes through the vertex of the V-dipole
antenna element and is equidistant from and coplanar with the axes
of the two legs of the V-dipole antenna element) and an angle x of
20 degrees with respect to the plane X that is perpendicular to the
central axis Y. Although an angle y of 70 degrees is illustrated in
FIG. 5B, the angle y may range from 20 to 90 degrees (i.e., the
angle x may range from 0 to 70 degrees) in other embodiments.
Further, although the legs 522 of the V-dipole elements 520 extend
through the plane P in the embodiment of FIG. 5, in other
embodiments the entirety of the V-dipole elements 520 are on one
side of the plane P while remaining inside an imaginary cylinder C
having a cross sectional shape formed by the projection of an outer
perimeter of the coils of the PCB 510 on the plane X normal to the
central axis of the V-dipole elements 520.
[0026] Positioning the PCB 510 at a non-normal angle with respect
to the V-dipole antenna elements 520 reduces antenna coupling by
creating a time lag between received impulses in each of the
V-dipole antenna legs 522. Since the coupling at each leg and the
nearest portions of the PCB 510 are of different length scales, the
differential signal between the two is incoherent. The resulting
coupling is incoherent and displays little ringing in the received
GPR signal. Coupling between the portions of the coils on the PCB
510 that are perpendicular to the legs 522 of the V-dipole elements
520 (e.g., the crossbar 512) is minimized because of the
perpendicular relationship.
[0027] Referring now to FIG. 5A, it can be seen that the V-dipole
elements 520 are on one side of the crossbar 512 (i.e., the
elements 420 are on one side of a plane that passes through a
center of the crossbar 512, is perpendicular to the faces of the
PCB, and is parallel to an axis of the crossbar 512 in a direction
in which current flows in the crossbar 512). This is done in order
to minimize coupling between the V-dipole elements 520 and the
terminals (not shown in FIG. 4) of the PCB 510. In other
embodiments, V-dipole elements 520 are positioned such that their
legs 522 are on opposite sides of the crossbar 512.
[0028] The MD/GPR hybrid heads disclosed herein may be utilized in
any device, and in particular may be incorporated into a handheld
device that includes the hybrid head and other conventional
components such as signal generators to generate signals for
transmission by the MD transmit coil and the GPR antenna, a signal
processor and associated analog-digital converters to process
signals received by the MD receive coil and the GPR antenna, a
power supply, and appropriate interconnections between the
aforementioned components. Any conventional techniques known in the
art may be utilized to process such received signals. The handheld
device may further incorporate a display for displaying video from
the GPR and objects detected by the MD. When the hybrid head is
incorporated into such a handheld device, it may be wholly or
partially enclosed by a housing such as the housing 600 of FIG. 6.
Regardless of whether or not a housing is provided, the GPR antenna
elements and the transmit and receive coils of the hybrid head will
be mechanically connected, either directly to each other or to
another component and/or the housing (e.g., the mechanical
connections 610 of FIG. 6).
[0029] It will be apparent to those of skill in the art that
numerous variations in addition to those discussed above are also
possible. Therefore, while the invention has been described with
respect to certain specific embodiments, it will be appreciated
that many modifications and changes may be made by those skilled in
the art without departing from the spirit of the invention. It is
intended therefore, by the appended claims to cover all such
modifications and changes as fall within the true spirit and scope
of the invention.
[0030] Furthermore, the purpose of the Abstract is to enable the
U.S. Patent and Trademark Office and the public generally, and
especially the scientists, engineers and practitioners in the art
who are not familiar with patent or legal terms or phraseology, to
determine quickly from a cursory inspection the nature and essence
of the technical disclosure of the application. The Abstract is not
intended to be limiting as to the scope of the present invention in
any way.
* * * * *